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What is a Plant Disease?  A disturbance that interferes with a plant’s “normal” structure, function, or physiological processes.  As opposed to a tree injury which is caused by a single event (e.g. hatchet blow to a tree)

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Disease Definitions   Parasite – an organism that lives on or in another organism.   Host – an organism that provides nutrition for an invading parasite.   Pathogen – an agent that causes disease.

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Control of Foliage Diseases  Control usually not needed nor is it practical  Maintain mixed species composition in stand  Maintain healthy, vigorous trees  Role of fire?  High value trees – both protective and controlling fungicides

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Cankers – a symptom of disease Localized area of dead bark or cambium –Often sunken because the tree continues to expand around the infection site Very common –More common on thin-barked species (aspen) Usually caused by fungal infections that enter through wounds

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Spread and Intensification  Plants tend to build up in bottom of crown and move up the crown  Mortality usually occurs from top down  Spread is quickest from an infected overstory to adjacent reproduction

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Ethephon (Chemical Name) –Also marketed under the trade name of “Florel” Causes abscission of dwarf mistletoe shoots preventing the development of fruit and seeds. Chemical Management of Dwarf Mistletoes

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What Are Decline Diseases? Decline diseases are caused by the interaction of a number of interchangeable, specifically ordered biotic and abiotic factors which produce a gradual general deterioration, often ending in the death of trees.

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Size up snag hazards in work area. Never become complacent. Always look up. Get weather reports. Scout out parking, sleeping, work areas, and safety zones. Advise co-workers of known hazards. Face your hazard and take appropriate action. Examine work area for other hazards. Take extra caution around heavy equipment. You are ultimately responsible for your own safety. SNAG (Hazard Tree) SAFETY: